Add new UMA stats to get a handle on Downloads UI Usage

chrome/browser/history/history_backend.h

Index: chrome/browser/history/history_backend.h
diff --git a/chrome/browser/history/history_backend.h b/chrome/browser/history/history_backend.h
index 19421cb90262ceb252efe88686d340dca6376385..757cf3b60114e5beb9fe8161ec70f6dd8d431ef3 100644
--- a/chrome/browser/history/history_backend.h
+++ b/chrome/browser/history/history_backend.h
@@ -246,7 +246,7 @@ class HistoryBackend : public base::RefCountedThreadSafe<HistoryBackend>,
   void GetNextDownloadId(scoped_refptr<DownloadNextIdRequest> request);
   void QueryDownloads(scoped_refptr<DownloadQueryRequest> request);
   void CleanUpInProgressEntries();
-  void UpdateDownload(int64 received_bytes, int32 state, int64 db_handle);
+  void UpdateDownload(DownloadItemData data);

[brettw, 2011/10/01 16:45:45]

This should be a const ref. The runnable methods know to copy const refs when
sending to the background thread, but you're requiring yet another copy for it
to call your function.

[benjhayden, 2011/10/03 20:54:39]

Done.

   void UpdateDownloadPath(const FilePath& path, int64 db_handle);
   void CreateDownload(scoped_refptr<DownloadCreateRequest> request,
                       int32 id,